You seem to be learning how to do programming in C#.
Maybe you should look up some tutorials online.
Currently you have a form with a driver and a BasicButton control on it.
Adding any more controls in the future will not make it any simpler for you.
There are some online code conversion tools which convert VB to C#, like this one:
https://www.carlosag.net/tools/codetranslator/You could also use SharpDevelop 4.4 program which has code converter built-in.
As for C# in AdvancedHMI, you need to be using the MainForm inside the AdvancedHMIcs project.
You also need to get familiar with Properties window, like the attached picture shows.
Lightning Bolt icon will show all events associated with selected object, whether it's a form or a control.
Double-clicking any of the events will create a code for you and take you to the code window.
If you manually add a code that you find somewhere online then you still need to associate that code with the event by selecting it in the properties window.